DCC in coreless motors
DCC in coreless motors
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So what is a coreless motor and why should I worry? Coreless motors do not have the usual laminated steel poles around which the armature windings are wrapped. Instead, the armature consists solely of the windings, which look rather like a woven basket (hence the slang term "basket wound" motors.) In regular motors, the laminated core serves to closely couple the magnetic field of the armature to the magnetic field of the field magnet surrounding the armature. With coreless motors, the magnetic field of the armature is closely coupled to a pair of magnets, one inside and one outside the winding. Advantage of a coreless motor is that the magnetic field in which
the armature rotates is stronger, making a more efficient motor.
I once saw a demonstration of their efficiency in which two coreless motors
were wired together. Turning one motor one complete turn by hand
generated enough electricity to turn the other eight tenths of a turn,
indicating an efficiency
Disadvantage of coreless motors is poor cooling. You are probably aware that you can run one engine without a decoder on a DCC system, but you cannot let it stand still for more than about ten minutes. You have that 10 minute grace period because it takes time to heat up the iron in the core. With a coreless motor, heating is virtually instantaneous and running a coreless motor on DCC without a decoder will fry it. Even with a decoder heating may be a problem. Lacking an iron core, the inductance (resistance to the flow of a.c.) of a coreless armature is low, so the a.c. component of the pulses fed to the motor by a decoder can heat the motor unless the frequency of the pulses is high. So called "stealth" decoders can be operated at higher pulses rates, so should be a good choice. As far as which engines have coreless motors, the only ones I have run into were in LGB G-scale engines. Maybe someone can enlighten us as to which engines in small scales might have coreless motors. |